1. The Field of the Invention
The invention generally relates to fiber-optic networking components. More specifically, the invention relates to fiber-optic components that allow for optical networking hardware to be implemented on computer systems.
2. Description of the Related Art
Computer processing power and speed continues to advance at an amazing rate. However, the continued growth of power and speed is not unexpected. In 1965, Gordon Moore predicted that the number of transistors, and hence the processing power and speed of computer chips, would double every couple of years. This predicts an exponential growth in processing power and speed. This prediction has been referred to as Moore's Law. Moore's law has generally held true.
In a modern computer, the microprocessor has several support components. For example, the microprocessor is connected to memory where the memory is used to store data, computer instructions and the like. For processing power and speed increases to be useful in a microprocessor, the speed of supporting components should scale with the processing power and speed of the microprocessor. For example, if memory connected to the processor is too slow, the processor must remain idle while fetching instructions or data from the memory. Thus, the increased processing power and speed of the processor is wasted.
Computer microprocessors and much of the supporting circuitry is based on silicon chip technology. At present, microprocessors and the supporting circuitry have generally scaled fairly well together. Best estimates also suggest that silicon based computers still have 10 to 15 years of processing power and speed increases if following Moore's Law.
One especially useful implementation of modern computers involves the interconnection of computers for transferring and sharing data between the computers. A small or moderate number of computers may be grouped together in a given location. This type of network is known as a local area network (LAN). LANs may be connected to other LANs to form a wide area network (WAN). An example of this type of configuration is shown in FIG. 1 which illustrates a topology 100 with a number of interconnected computer clients on LANs and WANs. Exemplary LANs include home networks, local office network and the like. Exemplary WANs include interconnected office LANs and the ubiquitous Internet.
Referring now to FIG. 1, a first LAN 102 includes a number of clients 104 interconnected by router 106 (also referred to herein as a “hub 106”). The LAN 102 in FIG. 1 uses copper wire based Ethernet, such as the protocol specified in IEEE 802.3. The LAN 102 is connected to a second LAN 108. The LANs 102 and 108 are connected in the example shown in FIG. 1 by routers 110 that are designed to send and receive large amounts of data. The routers 110 may be for example Huge Fast Routers (HFRs) and the like. In the example shown in FIG. 1, the routers 110 are interconnected using fiber-optic communications as shown by the fiber-optic links 112.
The second LAN 108 includes a number of clients 112. The clients 112 may be similar to the clients 104 in the first LAN 102. The second LAN 108 also includes a storage area network (SAN) 114 and a network of servers 116. The SAN 114 and network of servers 116 provide centralized locations for data that may be used by clients 104, 112 on the first LAN 102 and second LAN 108. Accessing data on the network of servers 116 and SAN 114 should ideally be transparent to users at the client computers 104 and 112. In other words, a user at a given client in the topology 100 should not experience any noticeable difference when accessing data on either any other client in the topology, the network of servers 116, or the SAN 114 as compared to when accessing data stored on the given client itself.
Referring now to the first LAN 102 for ease of explanation, the clients 104, as mentioned above, are interconnected through a hub 106 using an Ethernet protocol. A common Ethernet protocol is 100 BT that runs at 100 megabits per second (Mb/s). Alternatively, the clients 104 may be interconnected using a wireless protocol such as 802.11g which runs at around 56 Mb/s
Currently, there also exist systems that operate at 1000 Mb/s. These systems are called Gigabit Ethernet systems. Ethernet systems that use copper wire are quickly approaching their useful limit. As the data rate increases, the useful distance that data may be transmitted across the copper wire decreases. Alternatively, the cables used for interconnecting computers become expensive or difficult to install.
Likewise, wireless Ethernet alternatives are limited by frequency. Various regulatory organizations such as the FCC limit the frequency range in which wireless signals may be transmitted. Limited frequency range translates directly into limited bandwidth. Consequently, Ethernet applications based on copper wire or wireless implementations have limited data rates.
Some experts have suggested that Gigabit Ethernet is as fast as copper wire systems will operate efficiently. Wireless systems are also quickly approaching their limits as far as bandwidth is concerned. Thus, while silicon chip technology still has ample amounts of growth potential, it is anticipated that the conventional network systems that commonly interconnect silicon chip systems have reached (or are quickly reaching) their maximum potential.
As mentioned previously, modern computer systems use network information. In fact, much of the data used by a computer system is typically stored away from the computer system on a network device. As noted above, it is desirable that fetching of network information from the network be transparent to a computer user. However, if network speeds are significantly lower than computer system speeds, fetching the data will not be transparent. Thus, faster networks are needed to scale with computer processing speed as computer processing speed increases.
As shown in FIG. 1, LANs may be interconnected using fiber-optics such as the fiber-optic links 112 between the routers 110. Fiber-optic networks can operate at much higher data rates than copper wire or wireless networks. However, while the fiber-optic networks can transmit data between LANs at high speeds, a bottleneck still remains because of the copper wire or wireless based connections at the LANs themselves. Further, the routers interconnecting various LANs (as well as the routers at the LANs themselves) implement a function where the router collects an entire subset of data before transmitting it to a target network or computer system. This is commonly referred to as store and forward. This results in a bottleneck where all of the data for a packet or other subset of data is collected before forwarding to the next point (such as a router) in a network. Thus, the more conventional routers (whether copper wire or fiber based) that are used in a network, the more delay is caused by the cumulative effect of the store and forward operations.
Fiber-optic LANs, where each computer has a fiber-optic connection for connecting to the LAN, help to eliminate some of the problems described above. To connect to a fiber-optic LAN, each computer has a transceiver. The transceiver includes a laser for generating an optical signal. The laser is connected in the transceiver to a laser driver. The laser driver is further connected to other control circuitry in the transceiver. The transceiver receives a digital signal. The digital signal is processed by the control circuitry to improve the quality of the signal such as by removing noise and jitter. The laser driver converts the processed signal to an analog driving signal for modulating the laser output with the digital signal.
The transceiver also includes a photodiode that is included in circuitry for receiving optical signals and converting them to digital signals. The photodiode is connected to a transimpedance amplifier to boost the strength of the electrical signal produced when photons from the optical network signal strike the photodiode. Following the transimpedance amplifier is a post amplifier. The post amplifier further amplifies and feeds the signal from the transimpedance amplifier to other circuitry that is included to process and convert the electrical signal to a digital signal for use by a computer on which the transceiver is installed.
Transceivers are more expensive to manufacture than traditional 802.3 copper wire interfaces and thus have not widely been implemented on computers within a LAN. Thus copper or wireless LANs continue to be those most used. Because copper and wireless based communications will soon be the bottleneck in LAN connected computer system, it would be useful to provide methods and apparatus to lessen the cost of implementing fiber-optic communications on computer systems.